docs: def remove_page_boundary_lines(docbody):
      """Try to locate page breaks, headers and footers within a document body,
         and remove the array cells at which they are found.
         @param docbody: (list) of strings, each string being a line in the
          document's body.
         @return: (list) of strings. The document body, hopefully with page-
          breaks, headers and footers removed. Each string in the list once more
          represents a line in the document.
      """
      number_head_lines = number_foot_lines = 0
      # Make sure document not just full of whitespace:
      if not document_contains_text(docbody):
          # document contains only whitespace - cannot safely
          # strip headers/footers
          return docbody
  
      # Get list of index posns of pagebreaks in document:
      page_break_posns = get_page_break_positions(docbody)
  
      # Get num lines making up each header if poss:
      number_head_lines = get_number_header_lines(docbody, page_break_posns)
  
      # Get num lines making up each footer if poss:
      number_foot_lines = get_number_footer_lines(docbody, page_break_posns)
  
      # Remove pagebreaks,headers,footers:
      docbody = strip_headers_footers_pagebreaks(docbody,
                                                 page_break_posns,
                                                 number_head_lines,
                                                 number_foot_lines)
  
      return docbody